1. Field of the Disclosure
The present disclosure relates to machines including a compressor controlling apparatus for controlling at least two compressors by using, for example, an inverter, and a controlling method thereof.
2. Description of the Related Art
In general, a compressor is a device for converting mechanical energy into compression energy of a compressive fluid, and is used in various machines. For example, machines using a compressor include a refrigerator, an air-conditioner, or the like.
The compressor may be divided into a reciprocating compressor, a rotary compressor, and a scroll compressor. In the reciprocating compressor, a compression space is formed between a piston and a cylinder, in which operation gas is sucked into or discharged from, and the piston linearly and reciprocally moves within the cylinder to compress refrigerant. In the rotary compressor, a compression space is formed between an eccentrically rotating roller and a cylinder, in which operation gas is sucked into or discharged from, and the roller eccentrically rotates along an inner wall of the cylinder to compress refrigerant. In the scroll compressor, a compression space is formed between an orbiting scroll and a fixed scroll, in which operation gas is sucked into or discharged from, and the orbiting scroll rotates along the fixed scroll to compress refrigerant.
The reciprocating compressor sucks, compresses, and discharges the refrigerant by linearly and reciprocally moving the internal piston within the cylinder. The reciprocating compressor may be divided into a recipro-type reciprocating compressor and a linear type reciprocating compressor according to how a piston is driven.
The recipro-type reciprocating compressor couples a crank shaft to a motor that rotates and couples a piston to the crank shaft to convert a rotational movement of a motor into a linear, reciprocal movement. Meanwhile, the linear type reciprocating compressor connects a piston to an actuator of a motor that linearly moves and reciprocates the piston by the linear movement of the motor.
The reciprocating compressor includes an electric motor unit generating driving force and a compression unit compressing a fluid upon receiving the driving force from the electric motor unit. As the electric motor unit, generally, a motor is commonly used, and the linear type reciprocating compressor uses a linear motor.
The linear motor directly generates linear driving force by itself, without the need of a mechanical conversion device, and thus its structure is not complicated. Also, the linear motor can reduce loss resulting from energy conversion, and since it does not have a connection portion which may cause a frictional contact or may be abraded, noise can be considerably reduced. Also, when the linear type reciprocating compressor (referred to as a ‘linear compressor’, hereinafter) is used, for example, in a refrigerator or an air-conditioner, a compression ratio can be changed by changing a stroke voltage applied to the linear compressor, so that it can be used to control varying a cooling capacity.
Meanwhile, in the reciprocating compressor, in particular, in the linear compressor, the piston reciprocally moves without being mechanically restrained, so if a voltage is abruptly excessively applied, the piston may collide with a wall of the cylinder or the piston may not advance due to a large load, thereby failing to properly perform compression. Thus, a controlling apparatus for controlling the operation of the piston with respect to the change in the load or the voltage is desirable.
As an example, a compressor controlling apparatus detects voltage and current applied to a compressor motor and estimates a stroke according to a stroke sensorless method to perform feedback controlling. At this time, the compressor controlling apparatus uses a triac or an inverter in order to control a compressor. The compressor controlling apparatus employing an inverter controls only a single compressor by using a single inverter.